Foreign entanglements are what get you into World Wars.
The Crash of 1929 made the country even more inward looking...The protectionism bills passed during that time prolonged the depression. While other countries armed themselves and madman grew in power the USA did nothing. Our foreign holdings taken at the turn of the century like the Philippines was understaffed, our navy was forgotten.
We were ill prepared for WW2 and could not project power around the world to stop it form starting......
For the last 70 years American’s engagement in the world has stopped another world war from starting. The wars have been brief and local. Do you think without the USA and NATO the USSR would be gone form the face of the world?